Trip free electrical cutout



M. B. WOOD TRIP FREE ELECTRICAL CUTOUT Filed Jan. 2l, 1960 Oct. 31, 1961 Inventor Morris l/ood .By his Attorney wf M w 4 0 o0 6 02 4 o0 oN0 4 5 M United States Patent Oii 3,007,018 Patented Oct. 31, 1961 ice 3,007,018 TRIP FREE ELECTRICAL CUTOUT Morris B. Wood, 49 High St., Newburyport, Mass. Filed Jan. 21, 1960, Ser. No. 3,809 Claims. (Cl. 200-116) The present invention relates to overload cutouts for use in place of fuses in protecting electrical circuits, and more particularly the invention is concerned with a tripfree cutout, which is characterized by its ability to open a circuit automatically and to be closed manually while not requiring any facility for returning the circuit to opened condition thereafter, the cutout otherwise meeting all the essential requirements for stability, reliability, compactness and ease of manufacture and assembly.

Cutouts heretofore developed have had several common faults, notably incapability of opening a circuit to be protected with a tripfree action whenever the cutout is held in closed position manually. 'If capable of being actuated automatically to open a circuit whenever held closedmanually, then the mechanical features of the cutout have been found to be overly complex and delicate in adjustment or more than a single spring only is required, so that manufacture by mass production procedures usually is diflicult or reliability and durability are reduced from spring weakness or overstress.

A primary object of the present invention is to provide an overload cutout for limiting the current capacity of an electrical circuit, in which the drawbacks noted above have largely been eliminated and by means of which Va construction is aiforded lending itself to simple mass production procedures with attendant benefits of direct adjustments and absence of necessity for delicate manipulations likely to result in substandard results.

In the accomplishment of the primary and other objects, the features of the invention reside in a cutout having a box-like frame providing a guideway, a manually actuatable button mounted for lengthwise movement in the guideway, a carrier movable along the button, a contact fixed in the frame, another contact movable with the carrier in the frame to enable engagement with and separation from the xed contact, a thermostatic latch connected electrically with the iixed contact and a detent so pivoted to the carrier that it is engageable with the latch at a point along the length of the detent remote from the pivot point, in which cutout there is provided a fulcrum fixed to the frame at such a location that when the button is depressed the fulcrum engages the detent at a point along its length between the pivot point and the point of. engagement with ,the latch to cause the latch engaging point on the detent to move toward latched position in a direction opposite to that of the contact carrier. The advantage of this construction is that it avoids the` necessity of mounting the thermostatic latch on the contact carrier, as has been required in many prior cutouts, so that being 4fixed on the frame in the present arrangement the thermostatic latch is susceptible to direct and easy adjustment, whereas when mounted on the contact carrier the thermostatic latch must be adjusted relatively to another moving part. ASuch -adjustment frequently is inconvenient and is subject to likelihood of impermanence. t

p These and other features of the invention, kas hereinafter described and claimed will readily be apparent by those skilled inthe art from the following detailed description, taken in connection withV the accompanying drawings, in which:

FIG. l is a detail sectional view in front elevation of a cutout embodying the features of the present invention, portions in one of a pair of hollowwshell frame members being broken away to disclose the internal construction and the contacts being closed;

FIG. 2 is a sectional view of the cutout, not broken away, showing the contacts open after the occurrence of an overload;

FIG. 3 is a sectional view of the cutout broken away as in FIG. 1, with the parts shown in positions after being reset manually but before the contacts are again closed;

FIG. 4 is a sectional view, taken along the line IV IV of FIG. l, to illustrate both shell shaped frame members together in the complete frame enclosure.

The cutout of the invention is intended to limit the electrical current flow in a circuit to be protected and comprises a box-like frame composed of two shell-shaped insulating members 10 and 12, disposed with their open sides together and secure in registering relation by rivets 14, Within semicircular recesses in the upper side walls of the frame members is disposed a threaded collar 16 provided with a necked portion within which the side walls of the shell members iit to hold the collar in position. The collar comprises a cylindrical guideway within which is slidingly mounted for lengthwise movement a manually actuatable molded plastic button 18 having one end projecting from the frame and guideway. Within the frame the button is formed with suitable hollow enlargements at its lower end to accommodate other parts of the cutout and when depressed by applying downward manual force to the button, causes the cutout to be reset after having acted automatically to open the circuit. 'If the circuit connected with cutout still is such that an excessive current will flow it is impossible to cause the circuit to be closed for more than an instant by any manual operation of the button and once the circuit is closed there is no provision for opening it manually again, which characteristics distinguish the apparatus herein disclosed as a tripfree cutout.

Within the frame 10, 12 is a pair of contacts 20 and 22 carried by plates 24 and 26 fixed to a pair of internal enlargements 28 on the frame members at opposite sides of the button 18. Cooperating with the fixed contacts 20 and 22 are a pair of movable contacts 30 and 32 mounted on a carrier 34 movable along the button 18.

The contact carrier 34 is constructed from a length of at bar stock bent into the form of U-shaped base with laterally extending arms on which the contacts 30 and 32 are secured. The carrier has the base of its U-portion passing through opposed slots in the hollow end at the button, one of which slots is shown at 36 in FIG. 4. 'I'he contact carrier is normally pressed yielding away from the fixed contacts by a compression coil spring 38 disposed within the hollow end of the button 18.v The spring 38 is compressed at its upper end against the end of the hollow in the button and at its lower end against the base of the carrier. 4

In prior tripfree cutouts arranged to prevent holding a circuit closed manually whenever overload conditions exist, more than one spring is required to open the contacts and thereafter to enable closing the contacts yieldingly the circuitopening spring is made stronger than the circuit closing spring to counterbalance its force. In the cutout of the present invention the spring 38,is the onlyone required for accomplishing both functions. To produce yboth functions from a single spring the force at its lower end is modified by a lever of the rst class whi-le the upper end of thespring, acting directly on t-he button overcomes that required to compress the lower end of the spring through the lever. 4

In the invention illustrated, the force modifying lever consists of a detent 40 in the form of ,an elongated steel strip, the width of which extends diametrically through the opposed slots 36 and acrossv the button 18. The'detent is pivoted at one end point along its length to the button, a forked clip 42 ybeing attached to the lower end of the button for this purpose. For pivoting the detent on the clip 42 the left end of the detent is bent into a circular -loop through a slot in an upstanding portion of the clip and about a narrow integral bar dening the slot on the clip. The clip 42 extends to the right along the lower edges of two parallel sides on the lower portions of the b-utton 18, the parallel sides being all that is left of the button after cutting the slots 36 through. The slots 36 terminate at their upper ends in shoulders 44, one of which is shown in FIG. 4, toward which the detent 40 presses the contact carrier -at all times under normal operating conditions by reason of pressure exerted through the clip 42 on the detent by the spring 38. To attach the clip 42 to the button 18 the clip is formed with upwardly bent rectangular tabs iitting similar shaped recesses in the sides of the button and the tabs are secured to the button by rivets 4S. To cause the contact carrier 34 to be pressed toward the shoulders 44 by the detent 40, the detent at another point along its length, preferably at its right free end, remote from the pivot point is engaged by a hooked lower end of a thermostatic bimetallic latch 46. The latch extends upwardly along one side of the frame in a slight curve and has its upper end iixed to an upwardly extending arm of the plate 26, by which the thermostat is fixed on the cutout frame and `also connected to the contact 22.

By the construction described the latch 46 forms a fixed abutment about which the detent swings as the button, after being depressed manually, is released while the detent engages the latch. When the button is being released an upwardly deflected intermediate portion of the detent between its pivot and the point of engagement with the latch bears yagainst the under s-ide of an insulating sheet 48 fastened to the contact carrier 34. Under this condition the contacts remains open while the contact carrier is held in a lowered position by engagement with the shoulders 44 on the button. As the button continues to be released the shoulders 44 move away from the contact carrier and the spring 38 begins to expand. However, since the spring 38 bears on the upper end of the hollow in the button, its upper end rises with the button faster than the carrier, the carrier being engaged by the intermediate portion of the detent. The latch engaging point on the `detent being retained for swinging movement and the pivot point on the clip 42 moving with the carrier, the intermediate portion moves more slowly than the button and the upward force of the spring aga-inst the button predominates. The upward movement of the button then continues until an enlarged external lip 50 on the button engages the upper end of a counterbore in the frame through which the button passes. By this time the movable contacts 30, 32 have engaged the iixed contacts 20, 22 and the circuit through the cutout is closed (FIG. l).

The contacts in the cutout are retained in closed positions by the latch 46 until the electrical current iiow through the circuit to he protected becomes excessive. Upon the occurrence of excessive current flow the thermostatic latch 46 is heated and moves away from the detent, releasing it and enabling the spring 38 to move the carrier 34 downwardly to open the contacts. When the contacts are opened, as in FIG. 2, the button moves upwardly a short distance to expose a band of contrasting paint 52 as a sign of an open circuit. It now remains for the detent to be relatched.

To relatched the detent 40 after the circuit through the cutout is interrupted automatically by excessive current ow the button 18 is depressed to its lowermost limit (FIG. 3). In depressing the button 18 the clip 42, to which the detent is pivoted is moved toward the lower end of the frame. As the button is moved toward the lower end of the frame, the detent tirst engages the upper end of a fixed fulcrum in the form of a headed pin S4 projecting upwardly from the lower end wall of the frame. To secure the pin 54 in place its head is disposed within two registering opposed recesses in the lower end portions of the frame. As the button is depressed further the fulcrum pin acts within a seat 56 (FIG. 3) provided by an intermediate depression at the underside of the upwardly deiiected central portion of the detent.

The action of the fulcrum pin 54, being directly applied to the detent and engaging it at an intermediate point between its pivot point and its latch engaging point, causes the latch engaging point on the detent to move toward latched position in a direction opposite to that of the pivot point on the contact carrier, which supports it. As soon as the detent is latched the button may be released and the contacts retained in engagement. If the conditions which caused excessive current ow persist, the latch immediately releases the detent and the circuit is reopened, regardless of the movement imparted to the button.

Connected to the plate 24 and forming a part of it is a terminal extending downwardly from the contact 20 along the opposite side of the frame from the thermostatic latch 46 and through the lower end of the frame 10, 12. The circuit through the cutout runs from the terminal plate 24, to contacts 20 and 30, contact carrier 34, contacts 32 and 22, and -to therrnostatic latch 46. To the free end of the latch 46 is connected a flexible lead 58, running to a second terminal plate 60, also extending through the lower end of the frame.

To adjust the response of the thermostatic latch 46 to excessive current flow there is mounted in iixed position in the frame adjacent to the upwardly extending arm of the contact plate Z6 and the upper end of the latch, a screw 62 (see FIG. 3) passing through a threaded opening in a metallic insert 64. The insert 64 has a narrow ange disposed in registering grooved semicircular recesses, one of which is shown at 66 in FIG. l in the individual side walls of the frame shells 10 and 12. The inner end of the screw 62 bears against the upper end of the latch 46 and serves to bend the upwardly extending arm of the plate 26 more or less, thus changing the relation of the hooked lower end of the latch and the right end of the detent 40.

The nature and scope of the invention having been indicated and speciiic embodiment having been described, what is claimed is:

1. A trip free electrical overload cutout, having a box-like frame, a guideway in the frame, a manually actuatable button mounted for lengthwise movement in the guideway, a carrier movable along the button, contacts in the frame, one of which contacts is xed to the frame and another of which is movable and mounted on the carrier to be engaged and separated from` the ixed contact when the carrier is actuated, a thermostatic latch connected electrically with the ixed contact, an elongated detent pivoted to the carrier at one point along the length of the detent and engageable at another point along its length with the latch to retain the contacts in engagement, and a single spring only acting between the button and the carrier to open the contacts and to close them yieldingly in combination with a fixed fulcrum on the frame for engagement with the detent at -a position between its pivot point and its point of engagement with the latch to cause the latch engaging point on the detent to move toward latched position in a direction opposite to that of the contact carrier.

2. A trip free electrical overload cutout, as in claim 1, in which the button is hollow with the spring mounted for action within the hollow of the button.

3. A trip free electrical overload cutout, as in claim 2, in which the button has slots entering the hollow from the sides of the button and the detent passes through the slots in the button and extends laterally at either side of the button within the frame.

4. A trip free electrical overload cutout, as in claim 3, in which, the detent is in the form of a strip, the width of which extends diametrically across the button.

5. A trip free electrical overload cutout, as in claim` 1, in which, the contact carrier is U-shaped with laterally extending contact carrying arms, the base of the U passing through the slots in the button and being pressed yieldingly away from the xed contacts by the spring.

6. A trip free electrical overload cutout, as in claim 5, in which, there are two fixed contacts on the frame at opposite sides of the button and two movable contacts on the arms outside of the U of the carrier, the contacts being at opposite sides of the button.

7. A trip free electrical overload cutout, as in claim 3, in which the detent has a central depression forming a seat for the fulcrurn.

8. A trip free electrical overload cutout, as in claim 7, in which both the contact carrier and the detent pass through the slot in the button.

9. A trip free electrical overload cutout, as in claim 6, in which the thermostatic latch extends along one side of the frame and is connected to one of the two xed contacts and there are provided a terminal plate ex tending from the other xed contact along the opposite side of the frame and through vthe lower end of the frame, the button projecting through the upper end of the frame, a second terminal plate extending through the lower end of the frame and a flexible lead connected between the latch and the second mentioned terminal.

10. A trip free electrical overload cutout, as in claim 6, in which the frame is split to provide two open shells disposed with openings together and the fulcrum is in the form of a headed pin projecting upwardly from the lower end of the frame with the head disposed in registering recesses in the lower end portions of the frame.

References Cited in the file of this patent UNITED STATES PATENTS 2,073,103 Hodgkins Mar. 9, 1937 2,680,172 Moyer June 1, 1954 2,686,241 Straubl et al Aug. l0, 1954 2,701,829 Krieger Feb. 8, 1955 2,816,192 Ingwersen Dec. 10, 1957 

